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L. C. McEwen

Publications and source records attributed to L. C. McEwen.

11 recordsLinked to original sources
USGS2006

Organophosphate residues in grasshoppers from sprayed rangelands

Grasshoppers (Orthoptera) were collected in pastures that had been sprayed with malathion and acephate to estimate the secondary exposure of insectivorous birds to those pesticides. Residues of malathion were below 3 ppm at 30 and 54 hours after spraying and no malaoxon was detected. In contrast, acephate was found at 8 and 9 ppm 4 hours after spray; 3–5 ppm of the toxic metabolite methamidophos were also detected at that time. By 53 hours postspray, acephate levels declined to 2 ppm and methamidophos to less than 1 ppm. These results suggest that although malathion may not be a hazard to insectivorous species, acephate may be hazardous through metabolic transformation to methamidophos.

Chemistry and Ecology↗
USGS1986

Organochlorine contaminants in passeriformes and other avian prey of the peregrine falcon in the western United States

About 1,150 individuals of 38 species of Passeriformes and other small birds were collected in 1980 at 36 locations in eight western U.S. states for organochlorine (OC) chemical analysis. The bird carcasses (less beak, tarsi, gastrointestinal tract, and feathers) were combined by species and location (4 to 15 specimens per sample) into 124 composited samples for analysis. Also analyzed were 77 single specimens of four species, to assess variation in residue concentrations in individual birds. The chemicals detected (greater than 0.05 ppm) were the following (in order of frequency): DDE, polychlorinated biphenyls (PCBs), hexachlorocyclohexane (HCH), heptachlor epoxide, oxychlordane, dieldrin and toxaphene. DDE accounted for 72% of total OC concentrations (ppm DDE/ppm total OCs) overall and PCBs accounted for 3%. DDE mean (geometric) residues were highest in tree swallows ( Tachycineta bicolor Vieillot), 12.0 ppm; killdeer ( Charadrius vociferus L.), 5.9 ppm; and Brewer's blackbirds ( Euphagus cyanocephalus Wagler), 2.7 ppm. Eight migratory species showed mean DDE residues 13 times higher than those in four resident species (1.3 vs. 0.1 ppm, p < 0.05), but PCB residues were similar (0.03 vs. 0.02 ppm). Insectivorous species showed higher DDE, PCB and total OC residues than did either omnivores or granivores ( p < 0.05). Males of some species showed higher residues of DDE, PCBs and total OCs than did females ( p < 0.05). DDE residues, but not PCBs, in killdeer, Brewer's blackbirds and violet-green swallows ( Tachycineta thalassina Swainson) were significantly related (0.01 < p < 0.08) to latitude and longitude of origin. Concentrations of DDE in the carcass fat of some individual tree swallows and killdeer would be in the lethal range if 15 to 20% of the stored DDE were rapidly mobilized to the brain. Samples of 13 species contained DDE concentrations (greater than 3 ppm) considered sufficient to inhibit the normal reproduction of avian predators feeding on them. The evidence suggests that potentially harmful OC concentrations are present in certain western migrants and pose an even greater hazard to avian predators such as the peregrine falcon ( Falco peregrinus Tunstall).

Environmental Toxicology and Chemistry↗
USGS1986

Bird predation on cutworms (Lepidoptera: Noctuidae) in wheat fields and chlorpyrifos effects on brain cholinesterase activity

Horned larks, Eremophila alpestris (L.), and McCown's longspurs, Calcarius mccownii (Lawrence), were collected at intervals from two winter wheat fields in Montana after aerial application of chlorpyrifos to control cutworms. Both bird species had a high (95–100%) incidence of Lepidoptera, mostly pale western cutworms, Agrotis orthogonia Morrison, in their stomachs at 3 days postspray. Incidence of cutworms and other insects in stomachs of birds from sprayed fields was lower at 9 and 16 days postspray than in control birds, presumably due to insecticide-caused reduction of insects. Effects of birds on population dynamics of insect pests in wheat are unknown, but birds do contribute to cutworm mortality. Predation is one of the limiting factors to cutworm increase and can supplement insecticidal control. Brain cholinesterase activity in horned larks collected from the sprayed fields at 3 and 9 days postspray was significantly lower than in unexposed larks, but at 16 days the difference was not significant. Although nontarget birds clearly were exposed to chlorpyrifos and manifested a sublethal physiological response, toxic effects were lesssevere than those resulting from endrin application for cutworm control in wheat. More study is needed of larger chlorpyrifos-treated fields under a variety of conditions to fully assess effects on nontarget life.

Environmental Entomology↗
USGS1984

Organochlorine residues in eggs of black-crowned night herons from Colorado and Wyoming

Eggs of black-crowned night-herons Nycticorax nycticorax (L.) were collected for analysis from seven nesting sites in Colorado and Wyoming in 1979. One egg was taken per nest from as many as 20 nests per site during early incubation. The nests were marked and revisited after hatching, but before fledging, to record the number of live young. DDE was detected in all of the collected eggs (total 147) at a mean concentration of 3.1 ppm, fresh basis (residue means are geometric). Mean DDE at the seven sites varied from 1.8 to 7.6 ppm. Polychlorinated biphenyls (PCBs) were detected in 81 eggs (mean 1.0 ppm); the highest mean at any site was 2.2 ppm. Twelve other organochlorines were each detected in 1 to 30 eggs, usually at a concentration of > 1.0 ppm. Mean total organochlorines in the eggs from the seven sites ranged from 2.0 to 10.1 ppm and the median number of compounds per egg ranged from one to five. Eggshell thickness was negatively correlated (p > 0.001, r = – 0.585) with DDE levels in the 147 eggs. Average shell thickness (0.258 ± 0.030 mm) was 8.8% lower than the average thickness (0.283 ± 0.016mm) of 40 pre-DDT eggs from this region. The nesting sites with the highest DDE and total organochlorine residues in the eggs had the thinnest shells, produced the fewest young and had more nonviable eggs and dead young. At four of the seven sites, the average number of live young per nest was > 2.0, the minimum long-term mean required for population maintenance. The source of the contaminants found in the heron eggs in this study was not determined.

Environmental Toxicology and Chemistry↗
USGS1983

Effects on birds of fenthion aerial application for mosquito control

Effects on birds of an aerial application of fenthion, a potent organophosphorus cholinesterase (ChE)-inhibiting insecticide, were assessed on four study sites 1.8 to 3.6 km 2 in size. These sites were located within 121.5 km 2 of wet meadows treated with 47 g of fenthion (AI) per ha in ultra-low-volume formulation. Assessment methods were searches for sick or dead birds, measurements of brain ChE activity in specimens found dead or collected alive at different time intervals, and counts of bird populations. After treatment, 99 birds and 15 mammals were found sick or dead; 106 of these were on one site. Brain ChE activity in dead birds was depressed sufficiently to indicate that death was caused by an anti-ChE substance. Brain ChE activity in three common bird species collected alive showed the greatest reduction 2 days postspray. Two of these species had ChE activity that was still significantly ( P <0.05) depressed 15 days postspray. Bird populations declined most where mortality was heaviest. Fenthion sprayed for mosquito control was life threatening to many birds inhabiting treated meadows.

Journal of Economic Entomology↗